Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Program to build DFA that starts and end with ‘a’ from input (a, b) in C++
Given a DFA string of characters ‘a’ and ‘b’, which should start and end with the character ‘a’ the task is to find whether the string starts and ends with ‘a’ through a DFA.
What is DFA(Deterministic Finite Automata)?
In theory of computation, a branch of theoretical computer science, Deterministic Finite Automata is a finite state machine which accepts or reject strings of symbols. Deterministic refers to the uniqueness of the computation to run.
For finding the string by a DFA and the string should start and end with ‘a’ from the input (a, b). Since there is no concept of memory and we can only store the current character, the DFA can't store the string provided, else we can easily just check the first and last character of the sequence/string given to us.
Example
Input: a b b a Output: yes Explanation: The input string starts and ends with ‘a’ Input: a a a b a b Output: no
Approach we are following to solve the above problem −
So, we will make a DFA for the above stated problem and then will solve the problem according to the DFA we create.
dfa.jpg
Algorithm
Start Step 1-> In main() Call function srand(time(0)) to generate random numbers Declare variable as int max = 1 + rand() % 15 Declare and set int i = 0 While(i < max) Declare char data = 'a' + rand() % 2 Print data Increment i IF data = 'a' IF(i = max) Print "YES" End Loop While (i < max) Set data = 'a' + rand() % 2 Print data Increment i If (data = 'a' AND i = max) Print YES\n End Else IF(i = max) Print NO End End End Else Loop While (i < max) Set data = 'a' + rand() % 2 Print data Increment i End Print NO End End Stop
Example
#include <iostream>
#include <time.h>
using namespace std;
int main() {
// for generating random numbers
srand(time(0));
int max = 1 + rand() % 15;
int i = 0;
while (i < max) {
char data = 'a' + rand() % 2;
cout << data << " ";
i++;
if (data == 'a') {
if (i == max)
cout << "YES\n";
while (i < max) {
data = 'a' + rand() % 2;
cout << data << " ";
i++;
if (data == 'a' && i == max) {
cout << "\nYES\n";
} else if (i == max) {
cout << "\nNO\n";
}
}
} else {
while (i < max) {
data = 'a' + rand() % 2;
cout << data << " ";
i++;
}
cout << "\nNO\n";
}
}
return 0;
}Output
b b a b a b a b b b b b NO
708 Views
